The present invention relates to a radiant energy detection system for the angular location of a light-radiating object.
The invention finds a particular application in the field of the opto-electrical detection and the tracking of a target which emits light or is remotely illuminated and it is also applicable to automatic means for guiding a missile such as a semiactive homing head.
In such systems, an optical receiver focuses the useful radiation from the light-radiating object to be located onto a detecting device. The detector is usually associated with a moving mask which has transparent areas on an opaque background in various forms such as grids, optical tracks, sectors, etc. The combination of the detector and mask is calculated to allow the requisite location data to be obtained by processing the detected signals. These data are in general the co-ordinates of the image of the object in the detection plane relative to two cartesian reference axes X and Y, that is to say the elevation and bearing of the object, which correspond to the aiming error between the optical line of sight of the receiver and the direction in which the remotely situated object lies in the observed field.
There exist various embodiments of such systems, in which the detection device generally consists of a plurality of detecting elements. For example, an array of detectors lies in one of the reference directions X and Y and an array of slots or an optical track is movable in the second direction of measurement. The detection device may contain a single optical element provided that the mask incorporates a plurality of different optical tracks.
According to other embodiments, the detector device comprises four detection quadrants and there is no associated mask, processing on the four detection channels being by sum and difference formation to enable the requisite divergence values to be obtained.
An object of the invention is to provide a location system of low cost and fairly simple design which can be installed on board a moving object, such as a homing head for example, so as to operate in particular on a light-radiating object which may be formed by a source emitting light pulses. In this case, the system includes a detector which has only one photosensitive element and which is associated with a particular mask produced in a static form.
In accordance with a feature of the invention, there is provided a radiant energy detection system for the angular location of a light-radiating object, combining: an opto-electrical receiver comprising an optical arrangement for focussing the radiation from the said object onto a photosensitive detector element centered on the optical axis through a mask device which is controlled by an associated electrical control circuit. There are also provided circuits for processing the detected signal to generate signals representing the divergences in bearing and elevation for the object being aimed at; the said mask being a static device controlled to present a configuration having a transparent area corresponding to n measurement quadrants (n being a whole number at least equal to 1 and at most equal to 3) and an opaque area formed by the remaining 4-n measurement quadrants. The control circuit provides four successive operating states which are distinguished from one another by a rotation of .pi./2 radians of the configuration around the optical axis, and the processing circuits including a switching circuit operated synchronously with the mask by the control circuit to connect successively the output of the detector element to four reception channels which supply a divergence measuring circuit.